Ecology Unit Part 3: Energy Transfer

All organism need energy to carry out essential functions –For example: growth, movement, maintenance & repair, and reproduction The ecosystem’s structure is affected by: –The amount of energy an ecosystem receives –The amount of energy that is transferred from organism to organism

Producers Are autotrophs –Which are organisms that make their own food Most of them are photosynthetic But some, like bacteria, use chemosynthesis –which is the process of using inorganic molecules to produce carbohydrates Examples of producers?

Measuring Productivity Gross primary productivity is the rate at which producers in an ecosystem capture the energy of sunlight by producing organic material –The organic material that is produced in an ecosystem is called biomass Net primary productivity is the rate at which biomass accumulates and is expressed in units of energy per unit area per year (kcal/m 2 /y) –It is calculated by taking gross primary productivity and subtracting the rate of respiration in producers

Productivity Varies Two factors determine productivity: –Light –The availability of nutrients

Consumers Are heterotrophs –Which are organisms that must eat other organisms to obtain energy Consumers are also grouped by the type of food they eat Examples of specific consumers?

Groups of Consumers Herbivores: only eat plants or producers Carnivores: only eat animas or consumers Omnivores: eat both plants and animals (producers and consumers) Detrivores: only eat decomposing plant and animal parts including feces Decomposers: break down dead or decaying plants and animals by starting the decomposition process

What Type of Consumer?

Energy Flow When one organism eats another, molecules are metabolized and energy is transferred Energy flows through an ecosystem from producers to consumers One way to follow the pattern of energy flow is to group organisms in an ecosystem based on how they obtain energy A trophic level indicates an organism’s position in a sequence of energy transfers

Food Chains & Food Webs A food chain is a single pathway of feeding relationships among organisms in an ecosystem A food web is the interrelated food chains in an ecosystem

Food Web

Energy Transfer 10% of the total energy consumed in one trophic level is incorporated into the organism in the next level Why is the percentage so low? –No transformation or transfer of energy is 100% efficient –There are also limitations of trophic levels